lemons contain high levels of vitamin C.
also known as ascorbic acid.
The levels in lemons are around 50 mg per 100g
on a par with oranges and around double the amount of limes.
Vitamin C deficiency can lead to scurvy,a disease that causes loss of teeth,jaundice and eventually death.
In the 1700s, all British ships were required to provide a lemon juice ratio to seamen to guard against this disease.